Every Japanese verb and adjective belongs to a Class (on the y-axis next page), which has one of six Stem Endings (on the x-axis next page) depending upon the function or suffix to be added to the verb or adjective.

To understand the structure of Classical Japanese inflected forms, let’s construct one. Let’s say we want to form the participle: having been invited.

We start with the verb sasohu – ‘invite,’ which is a 四段 verb, so looking at the table on the next page, we see that 四段 forms are:

and we apply them to the verb sasohu to produce:

We want to make the verb passive, so we check the List of Verbal Suffixes and find:
“Passive る after 未然 (四段,ラ,ナ); らる after 未然 (other Classes)”

sasohu is a 四段 verb, so we add る to the 未然形 form (in this case sasoha-), to form:
saso-ha-ru – ‘is invited.’

Now we want to make the verb perfect, so we check the List and find:
“Perfect (四)り after 已然; たり after 連用; つ after 連用; ぬ after 連用; り after 未然”

Lots of choices; let’s use the most common, つ after 連用, so we need to put る into 連用:
-ru takes 下二 endings, so ru becomes re

to produce: saso-ha-re-tsu – ‘has been invited’

Now we want to make it a participle (having been invited), and all verbs use 連用 for that, so we put -tsu (a 下二 suffix) into its 連用 form

to produce: saso-ha-re-te – ‘has been invited.’